The present invention relates to integrated circuits and, more particularly, to thermal protection systems for integrated circuits. A major objective of the present invention is to provide for thermal protection of an integrated circuit.
Much of modern progress has been based on integrated circuits of increasing speed and integration. Along with increased speed and integration has come increased power consumption, as well as increased heat dissipation. Additionally, some applications require high-power devices that can generate considerable heat despite a low level of integration. Ideally, the dissipated heat is removed as fast as it is generated. When heat is generated faster than it is dissipated, the temperature of the integrated circuit rises. In extreme cases, the heat can damage the integrated circuit and/or surrounding components.
The problem with handling dissipated heat is handled in part by designing circuits that generate relatively little heat for their given level of functionality. The increasing implementation of CMOS technology in very-large-scale-integration devices is due in part to its lower power requirements, and thus low heat generation. Even using such power-conserving technology, modern microprocessors consume over ten Watts. Removing the heat dissipated by such circuits can be problematic, especially where the integrated circuits are closely arranged in an enclosure with limited ventilation.
To assist heat removal, heat sinks have been attached to integrated circuits. Heat sinks are typically metal for good thermal conductivity. The heat sinks tend to have fins or other features that provide a relatively large surface area from which heat transferred from the integrated circuit can be radiated into the ambient air.
Heat sinks are considered passive cooling systems in that they require no power or control to function. Passive cooling systems are preferred for their simplicity, economy, and reliability. However, active cooling systems can be required where heat removal requirements are high. For examples, electric fans can be built into a heat sink. Other systems provide for circulating coolant. Water and even liquid helium or nitrogen cooling systems can also be used. Heat pipes are in development for integrated circuits that absorb the heat of vaporization by boiling a liquid, and then remove the vapor. However, all these active and circulating systems suffer cost, complexity, and reliability concerns.
Thermal protection circuitry can be used to protect circuit components when heat removal is inadequate. A heat sensor can trigger when local heat is excessive. The sensor can be coupled to a switch that turns off the power to the system incorporating the overheating device. However, even with the power shut off, accumulated heat can continue to affect system components adversely. This problem can be mitigated by setting the sensor trigger threshold at a level that is safe for continuous operation. However, this can cause the system to shut down more frequently than necessary.
What is needed is improved protection of integrated circuits from accumulated heat. Both improved heat sinking and thermal protection circuitry are desired.